21A Light Red 1.25" Telescope Filter - (25% transmission) Enhances Detail In The Belts And Polar Regions Of Jupiter and Saturn - Helps You See Mercury During Daylight Hours By Increasing The Contrast Between The Planet And The Blue Sky - Includes Clear Safety Case

• Eyepiece filters are an invaluable aid in lunar and planetary observing.
• They reduce glare and light scattering, increase contrast through selective filtration, increase definition and resolution, reduce irradiation and lessen eye fatigue.
• These filters are made of high quality, solid plane parallel glass with excellent homogeneity.
• They are anti-reflection coated to prevent glaring and ghosting.
• All eyepiece filters are threaded to fit most 1.25" eyepieces and offer a full 26mm clear aperture. Comes with a hinged, plastic case to keep your filter safe and clean when not in use.

#23A Light Red (25% transmission): On telescopes of 6" aperture and larger the #23A does approximately the same functions as the #21 filter, but with stronger contrast and enhancement of marginally defined blue-green surface detail. Useful primarily on Jupiter, Saturn, and Mars. Increases contrast between Mercury and bright blue sky during daylight observations or during twilight.